NAME

Kavorka::Manual::Functions - fun keyword

DESCRIPTION

Kavorka provides the fun keyword for the purpose of defining functions (as against methods, etc).

The anatomy of a function:

1. The keyword introducing the function.

2. The function name (optional).

3. The signature (optional).

4. Traits (optional).

5. The prototype (optional).

6. The attribute list (optional).

7. The function body.

Example:

#  (1) (2)    (3)          (4)     (5)   (6)     (7)
   fun foobar ($foo, $bar) is cool :($$) :cached { return $foo + $bar }

#          (1) (6)
   my $f = fun { return $_[0] + $_[1] };

The Keyword

This requires very little explanation. If you're no fun, and don't like the name fun, you can export it with a different name:

use Kavorka fun => { -as => 'function' };

The Function Name

If present, it specifies the name of the function being defined. If no name is present, the declaration is an expression that evaluates to a reference to the function in question.

Functions are automatically forward-declared; a la

sub foobar ($$);

but are installed into the symbol table at run-time. So this works:

if ($ENV{DEBUG}) {
   fun foobar { ... }
}
else {
   fun foobar { ... }
}

It is possible to install the function at compile time using the begin trait:

fun foobar but begin { ... }

It is possible to define lexical functions using a lexical variable for a function name:

fun my $add ($x, $y) {
   $x + $y;
}

my $sum = $add->(20, 22);

The Signature

See Kavorka::Manual::Signatures.

Traits

See Kavorka::Manual::ExtendingKavorka.

The Prototype

See Kavorka::Manual::PrototypeAndAttributes.

The Attributes

Attributes may alternatively be provided before the signature.

See Kavorka::Manual::PrototypeAndAttributes.

The Function Body

This is more or less what you'd expect from the function body you'd write with sub, however the lexical variables for parameters are pre-declared and pre-populated.

f, func, and function

These are all aliases for fun, though not exported by default.

use v5.14;
use Kavorka qw( function f );

function make_plusser (Num $x = 1)
{
   return f(Num $y) { $x + $y };
}

my $plusser = make_plusser();
say $plusser->(41);   # says 42

BUGS

Please report any bugs to http://rt.cpan.org/Dist/Display.html?Queue=Kavorka.

SEE ALSO

Kavorka::Manual, Kavorka::Manual::Signatures, Kavorka::Manual::PrototypeAndAttributes, Kavorka::Manual::MultiSubs.

AUTHOR

Toby Inkster <tobyink@cpan.org>.

COPYRIGHT AND LICENCE

This software is copyright (c) 2013-2014, 2017 by Toby Inkster.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

DISCLAIMER OF WARRANTIES

THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.

cpanm Kavorka

perl -MCPAN -e shell
install Kavorka